Telephone system



Dec. 8, 1931. F c 55555 1,835,003

TELEPHONE SYSTEM Filed March 20, l929 INVENTOR AFC-51 8562 ATTORNEY imposed current in the Patented Dec. 8, 1931 UNITED STATES PATENT OFFICE "FREDERICK C. BISBEE, OF ELIZABETH, NEW JERSEY, ASSIGNOR T AMERICAN TELE- PHONE AN D TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TELEPHONE SYSTEM Application filed March 20, 1929. Serial No. 348,497.

This invention relates to telephone systems and more particularly to telephone metering systems in which the subscriber is charged for V the length of time his telephone is in use.

' It is an object of this invention to provide 0 an improved telephone metering system in which maximum accuracy is attained in measuring the actual length'of time the subscribers telephone is in use and in which at the same time there is incurred minimum transmission loss, a minimum amount of I10lS6 in the talking circuit and minimum distortion of the voice signals.

The invention comprises in combination with a telephone system a synchronous alternating current motor bridged across each subscribers lines, registering apparatus adapted to be operated by said motor, means located at the central office for superimposing on the calling subscribers line alternating current of telephonically inaudible fre- ,quency" to operate the motor in the calling subscribers line, means located in the cord circuit for preventing'th'e flow of said super called subscribers lineand the operation of the motor located therein, and means located in the generator leads and in the motor leads for preventing the passage therethrough of voice signals with resultant transmission loss.

In the drawings, Figure 1 represents diagrammatically atelephone circuit illustrating one embodiment of the invention in which alternating current of a frequency above the range of telephonic audibility is superimposed on the line to operate a synchronous alternating current motor. Fig. 2 represents diagrammatically a telephone circuit illustrating another embodiment of the invention in which alternating current of a frequency below the range of telephonic audibility is superimposed on the line to operate the motor. 1

In Fig. 1, there are shown two subscribers i istations A and B with subscribers loops extending to the central oflice and terminating in the jacks 14 and14. Asshown, A represents the station of the calling sub scriber and B that of the called subscriber.

55.0 Thejsub-stations comprise the usual transto mitters 1 and 1', the receivers 2 and 2, the receiver hooks 3 and 3', the contacts 4 and 4 and 5 and 5, respectively, the induction coils 6 and 6, the ringers 7 and 7 and the condensers 8 and 8. In addition, there are located at the sub-stations synchronous alternating current motors M and M bridged across the subscribers lines through leads 9 and 9',respectively, condensers 10 and 10' and 28 and 28, respectively, and the contacts 11 and 11. The motors M and M have driving shafts 12 and 12' which, when rotated, drive the ratchet wheels 13 and 13. In order to facilitate starting, these motors may be of the split-phase type or may have shaded pole pieces, if desired. v

The cord circuit C of the central oflice is here illustrated as the impedance coil feed type. Obviously, cord circuit of the repeating coil feed type may be used, if desired. The cord circuit shown comprises the usual current source 15, grounded at 16, a current supply bridge comprising impedance coils 17, capacities 18 and 18, cord conductors 19, 19, 20 and 20 and supervisory relay 21. In addition, there is located at the central oflice an alternating current generator G which is adapted to generate alternating current of a frequency above the range of telephonic audibility. This current is adapted to be super imposed on the talking current, flowing in the calling subscribers lines, through the leads 22 and 22, the contacts 23 and 23, the armatures 24: and 24 and the leads 25 and 25. The time when and during which this current is superimposed on the calling line is underthe control of relay 21.

The expressions telephonically inaudible, above the range of telephonic audibility, and below the range of telephonic audibility as used in the description and claims should be understood as referring not only to frequencies which are normally inaudible to the naked ear of the listener but also to frequencies which are audible to the naked ear of the listener but which after being transmitted through the telephone system may not be audible to the ear of the subscriber.

In order to prevent the operation of the motor located at the call-ed subscribers station, a pair of inductances 26 and 26 are located in series with the cord conductors 19 and 20, respectively. These inductances are of such value, for example, of the order of .003 henries, "as to permit the passage therethroughof voice frequency signals but-prevent the passage therethrough of alternating current of a frequency above the range of teleph'on'icaiidibilityi (the iiietor operating current). In additionfc'ap'acitie's 27 f and 27,

which are located in series with theleads and 25, and capacities 10 and 10, and 28 and 28, which are located. inthe leads 9 and QQrespectively, are provided in order to prevent untliie tran'sii'ii ssion loss. These capacit-ies' a re offsiichvalue, for eminpl efthe order of Q1 mier'ofarads, as to permit the p assage V therethrough 6f alternating current of a" fre'quencyabhvetlie range "of telephonic libility'ibut prevent the passage theretlirough ofjvoiee frequency signals.

[F2 ofthe drawing discloses a system in which, as hitheito' st ated; alternating current of a frequency below' the "range of teleph f i c" ahdibility is" supei'iinposedon the tallying current in the calling subscribe1"s lines to operate 'a synchronous alternating eurrent Inotor fbi'i'dgedacrosssaid line. As shown in 3 tl'iisfi'gure, the elements 'and the arrangement. thereof are "similar-to those shotwnin'Fig. 1,"with the exception that in 'ei latealternatiiig current of a frequency be- .lowf'the mugs of telephonic"'audibility" and the mtmrs'Mjanaf-M'are designed to operate in I syiiclfronisinx therewith. Also, in this cin- "biidin'ieiit, in tine-rto pi-event the operation lof themotor located at the called su'bscribe1"s statiomthecapacities 18 and 18 ,'whibh are infse riiesf with the corchconductorsyare of ,sueh jvaliie,"foreXan1ple,- of the i order of 1 i nicrofaijadfas to penint the"pas'sage there- "fli eagh of voice frequency s'ignals'fbut prevent the tlieretlfrough of alternating current :of a frequency below the range of telephonic audibilityf motor 'o aerating eurrenty and in order to prevent undue transmission loss-,f filtering means including inet-atte ts? "and 27 and capacities 29 and 29', respectively, a r-e located inseries with .theleads 25 and25"; "Similar filtering means igelpuing incniaafiqes:e0; snso and 31iand capacities 10, 32, 10' and'*'32,' respectively, le'ads9"and' 9", respectively,

value *fach {filteris resonant to .al t eriiatihg rent of a frequencyjbelo'w the range gr telephonic audibility the motor :peratr'ng currentx but'is nonresoiiant to Thebperat'ion' of the 'system as shown-in Fig.1 is as follows:

"When 'thesiihsei-ibei -at statibn"Areinoves his receiver from the hook to initiate a call, the operator in response to the signal establishes a connection to the central ofiice in the well-known manner. At this time, the current flows from the positive terminal of the source-15, through the upper left impedance coil 17 ,the'inductance 26, the cord conductor 19, the jack 14, out over the calling subscribers loop through the transmitter 1, the receiver hook 3,1tlie"contact 5,induction coil 6, 'back'through the jack 14,the cord' conductor 20, the inductance 26' and the lower left impedance coil 17 to the negative terminal of the source 15. Although the contact 11 is closed ment of these connections effectively connects the generator G in the circuit-of the calling su'bscrl'bers line wan d supernnposes on 1 said line an alternating current of telephonically inaudible frequency; The :path traversed by this'cu-rrent includes the leads22 and 22 the contacts 23 and 23; the armatures 24 and 24,

-the"-leads'25 and'25,the-capacities 27 and '27, theJcordconductors 19-and 20, the jack 14, the calling-subscriberslines,- the leads 9; the capacities 10- and 28,'the contact 11,- and "the" Winding of the motor M. The motor M begins to operate, rotating the shaft 12 and the ratchet wheels 13 and continues todo so 'untilone of the subscribers returns his re- 0617GT to '1ts hook or the operator breaks the connection at the central office.

I Themotor M being, operatedlbya superimposed, telephonically' inaudible, alternating current,

will run withouthumming and .at a constant speed regardlessof fvarlations of'the current flowing in the lineand thus insure accurate time meas'ureinent. I Furthermore, the oper- --at1-ng current being of telephonlcally inaudible frequency, there will be no disturbance created in the talking circuit. 7 The. motor M located in the called subscribers line will not be: .operated due tothe fact that the inductances 26 and 26 will prevent the motor operating current from passing into his line.

The voice frequency signals are prevented "from passing through themotors M and M by capacities 10 and' 28and10 and 28,re-

spectively, or through-the circuit of thegenerator G bycapacities 27 and 27.

shown *ahd described, the generator is connected on one-side of the cord, circuit only since, 1n general, it'i-s desirable toicharge'the call to the calling subscriber only. It is obvious, however, that the same mechanism could be applied on the other side of the cord circuit or on both sides of the cord circuit, if desired. The generator G may be common to all of the cords of a given exchange or to a group of cords, or, if desired, may be supplied for each cord separately. Likewise, the association of the generator with the cord circuit may be under the control of other means than the relay 21 in such a manner that the operation of the motor will begin at any desired time during the connection.

While this invention has been illustrated in connection with a typical cord circuit used in manual operation, it is apparent that it is equally applicable to machine switching apparatus.

What is claimed is: I

1. In a telephone system, subscribers lines, an alternating current motor bridged across each of said lines, registering means adapted to be operated by said motor, connecting circuits including a source of current for'establishing talking connections between said lines, and a generator adapted to superimpose on said lines alternating current of telcphonically inaudible frequency to operate said motor, said motor being adapted to operate in synchronism with said generator.

2. In a telephone system, subscribers lines, a synchronous motor bridged across each of said lines and responsive to alternating current of telcphonically inaudible frequency, metering apparatus adapted to be operated by said motor, connecting circuits including a source of current for establishing talking connections between said lines, agenerator adapted to superimpose on said lines alternating current of telephonically inaudible frequency to operate said motor, and means for preventing the passage of voice frequency signals through said motor and said generator and for permitting the passage therethrough of alternating current of substantially inaudible frequency.

3. In a telephone system, a calling line and a called line, a synchronous alternating current motor bridged across said calling line, recording means adapted to be operated by said motor, connecting circuits including the source of current for establishing talking I connections between said lines, and generator means adapted to superimpose on said calling line alternating current of telephonically inaudible frequency to operate said motor.

4. In a telephone system, a calling line and a called line, a synchronous alternating current motor bridged across said calling line, connecting circuits including a source of current for establishing talking connections between said lines, a generator adapted to superimpose on said calling line alternating current of telcphonically inaudible frequency to operate said motor, and means for preventing the passage of voice frequency signals and direct current through said motor and said generator and for permitting the passage therethrough of alternating current of telcphonically inaudible frequency.

5. In a telephone system, a calling line and a called line, an alternating current motor bridged across said calling line, connecting circuit-s including a battery for establishing talking connections between said lines, a dynamo electric machine adapted to superimpose on said calling line alternating current of telcphonically inaudible frequency to operate said motor, said motor bein adapted to operate in synchronism with said dynamo electric machine, means for preventing the passage of voice frequency signals and direct current through said motor and said dynamo electric machine and for permitting the passage therethrough of alternating current of telcphonically inaudible frequency, and means for preventing the passage of alternating current of telcphonically inaudible frequency into said called line.

6. In a telephone system, a calling line and a called line, a synchronous alternating current motor adapted to be bridged across said calling line when the circuit of said calling line is closed, connecting circuits for establishing talking connections between said lines, a source of current for supplying talkin g current to said lines, a generator adapted to be connected in the circuit of said calling line and to superimpose on said calling line alternating current of a frequency above the range of telephonic audibility to operate said motor, said motor being adapted to to operate in synchronism with said generator, switching means controlled by the closure of the circuit of said called line for connecting said generator in the circuit of said calling line, inductance means in series with the circuit of said called line for preventing the passage of said superimposed generator current into said called line, capacitative means in series with said motor bridge for preventing the passage therethrough of voice frequency signals and direct current and for permitting the passage therethrough of said superimposed generator current, and means in series with said generator leads for preventing the passage therethrough of voice frequency signals and direct current and for permitting the passage therethrough of said superimposed generator current.

In testimony whereof, I have signed my name to this specification this 19th day of March, 1929.

FREDERICK C. BISBEE. 

